81 lines
3.2 KiB
Markdown
81 lines
3.2 KiB
Markdown
# Fork vs Threads Project Synopsis
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## Project Synopsis
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This project investigates the differences between process creation using fork() and thread creation
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using pthreads in Linux. The goal is to experimentally evaluate performance, scalability, and
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system limits. By measuring execution time, memory usage, and maximum creation limits, we aim
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to understand how the operating system balances efficiency and isolation.
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## Workload Distribution (4 Members)
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- **Ηλίας –** Theory & Background + CITATIONS!!!!: Write introduction and explain
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processes vs threads concepts.
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- **Ανδρέας & Διονύσης –** Experiment & Code: Implement all benchmarks and run
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experiments.
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- **Αντώνης –** Data & Visualization: Collect results and create graphs/tables.
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- **Ανδρέας & Διονύσης –** Analysis & Writing + CITATIONS!!!!: Write methodology,
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discussion, and conclusion sections.
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## Experiments Overview
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- [x] Creation Time Comparison:
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Measures how long it takes to create multiple processes using fork() versus threads
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using pthreads. This highlights the overhead differences between process and thread
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creation.
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- [ ] Recursive Fork Explosion:
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A process recursively calls fork() to observe exponential growth in the number of
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processes. This demonstrates how quickly system resources can be exhausted.
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- [x] Thread Recursive Scaling:
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Similar recursive creation using threads to compare scalability and resource usage against
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fork().
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- [x] Maximum Limit Stress Test:
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Continuously creates processes or threads until the system refuses further creation,
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revealing OS-enforced limits on concurrency.
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- [ ] Memory and Stability Observation(removed max forks with ulimit -u 20000):
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Monitors system memory usage and system responsiveness during heavy process and
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thread creation.
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## Key Findings Focus
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- Threads are expected to be faster and more scalable than processes. - fork() is heavier due to
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process isolation. - Recursive fork leads to exponential growth and system stress. - Threads share
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memory, reducing overhead but increasing complexity. - System limits prevent uncontrolled
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resource exhaustion.
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PS. See undefined behaviour from calling fork inside thread.
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Print stack on each fork bomb on each iteration.
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Citations will include:
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1. Man pages
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2. Linux kernel docs from IEEE
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3. Thread docs
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## Key Commands for lifting linux kernel restrictions on alpine linux for threads & processes:
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```
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# Lift shell nproc limit
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ulimit -u unlimited
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# Raise kernel PID/thread caps (temporary until reboot)
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sudo sysctl -w kernel.pid_max=131072
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sudo sysctl -w kernel.threads-max=131072
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# Lift cgroup v2 pids limit (temporary until reboot)
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sudo sh -c 'echo max > /sys/fs/cgroup/pids.max'
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```
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## Crash/Stress Behavior (Runner Env Vars)
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The runner script uses the following environment variables to control risky experiments:
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- `ALLOW_DANGEROUS=1` to enable `fork_bomb` and `max_limit_stress` (default: 0).
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- `FORK_BOMB_SECONDS=<seconds>` to timebox `fork_bomb` runtime.
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- `MAX_LIMIT_SECONDS=<seconds>` to timebox `max_limit_stress` runtime.
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Example:
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```sh
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ALLOW_DANGEROUS=1 FORK_BOMB_SECONDS=5 MAX_LIMIT_SECONDS=5 bash run_all_experiments.sh
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``` |